Kepler-11e
Encyclopedia
Kepler-11e is an exoplanet
(extrasolar planet) discovered in the orbit of the sunlike star Kepler-11
. It is the fourth of six planets around Kepler-11 discovered by NASA
's Kepler spacecraft. Kepler-11e was found by using the transit method, in which a the dimming effect that a planet causes as it crosses in front of its star is measured. Kepler-11e is most likely a gas giant
like Neptune
, having a density that is less than that of Saturn
, the least dense planet in the Solar System. Its low density can probably be attributed to a large hydrogen and helium atmosphere. Kepler-11e has a mass eight times of Earth's mass and a radius 4.5 times that of Earth. The planet orbits its star every 31 days in an ellipse that would fit within the orbit of Mercury
. Kepler-11e was announced on February 2, 2011 with its five sister planets after it was confirmed by several observatories.
-157. It was later assigned the name "Kepler-11" after the Kepler spacecraft, a NASA
satellite tasked with discovering planets in transit of, or crossing in front of, their stars. This transit causes a slight and regular change in the host star's brightness, which can then tested to prove the planet's existence and, later, to extrapolate the orbital parameters of the planet. Kepler-11e is first given the designation by its host star, Kepler-11. Since Kepler-11e was announced with five other planets, the letters added to the star are sorted by the planet's distance from its star. Kepler-11e is the fourth planet from Kepler-11, it is given the designation "e".
Follow-up confirmation observations were made by the Keck 1 telescope at the W.M. Keck Observatory in Hawaii, the Hale
and Shane
telescopes in California, the Harlan J. Smith
and Hobby-Eberly
telescopes in west Texas, the Nordic Optical Telescope
in the Canary Islands, and by telescopes at the WIYN
(including MMT
) and Whipple
observatories in Arizona. The Spitzer Space Telescope
was also used. Kepler-11's planetary system became the first discovered extrasolar system with more than three transiting planets, as well as the most compact and flattest system yet discovered, according to NASA. The planets of Kepler-11, including Kepler-11e, were announced jointly at a press conference on February 2, 2011. The findings were published in the journal Nature
on February 3.
. It has a mass of .95 Msun
and a radius of 1.1 Rsun, and is thus almost the same mass and radius as the Sun. With an effective temperature
of 5680 K, it is also almost as hot as the Sun, and with a metallicity
of 0, Kepler-11 is almost as metal-rich as the Sun is. Metal-rich stars tend to have easily detectable planets because higher metallicities tend to either facilitate the creation of gas giants or to promote planetary migration
, in which the planet orbits more closely to its star. However, Kepler-11 is almost 1.73 times older than the Sun, as it has an estimated age of eight billion years. Kepler-11 is 613 parsec
s away from the Earth; its distance contributes to its apparent magnitude
of 14.2 (V). It, thus, cannot be seen with the naked eye
. Other than Kepler-11e, Kepler-11 is the host star of the planets Kepler-11b
, Kepler-11c
, Kepler-11d
, Kepler-11f
, and Kepler-11g. The inner five planets in the system orbit in a tightly knit configuration that would fit within the orbit of planet Mercury
, while Kepler-11g, compared to its inner sister planets, orbits at a much further distance.
at standard temperature and pressure
and slightly less than the density of Saturn. Kepler-11e has a surface equilibrium temperature of 617 K, and is thus has an equilibrium temperature approximately 2.4 times hotter than Earth's. Kepler-11e orbits its star at a mean distance of .194 AU
, making it the fourth planet from its star. It completes an orbit every 31.995990 days. In comparison, Mercury
orbits the Sun every 87.97 days at a distance of .387 AU. Kepler-11e's orbital inclination
is 88.8°, making it almost entirely edge-on to its star as seen from Earth.
Because it isn't as close to its star as its sister planets Kepler-11b
and Kepler-11c
, the Kepler team suggests that its light density may come from a large hydrogen and helium atmosphere that has not been blown away by the stellar wind
.
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
(extrasolar planet) discovered in the orbit of the sunlike star Kepler-11
Kepler-11
Kepler-11 is a sun-like star slightly larger than the Sun in the constellation Cygnus, located some 2,000 light years from Earth. It is located within the field of vision of the Kepler spacecraft, the satellite that NASA's Kepler Mission uses to detect planets that may be transiting their stars...
. It is the fourth of six planets around Kepler-11 discovered by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Kepler spacecraft. Kepler-11e was found by using the transit method, in which a the dimming effect that a planet causes as it crosses in front of its star is measured. Kepler-11e is most likely a gas giant
Gas giant
A gas giant is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in the Solar System: Jupiter, Saturn, Uranus, and Neptune...
like Neptune
Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...
, having a density that is less than that of Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
, the least dense planet in the Solar System. Its low density can probably be attributed to a large hydrogen and helium atmosphere. Kepler-11e has a mass eight times of Earth's mass and a radius 4.5 times that of Earth. The planet orbits its star every 31 days in an ellipse that would fit within the orbit of Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
. Kepler-11e was announced on February 2, 2011 with its five sister planets after it was confirmed by several observatories.
Name and discovery
When Kepler-11 was first noted as a host to a potential transit event, the star was given the designation KOIKepler Object of Interest
A Kepler Object of Interest is a star observed by the Kepler spacecraft which is suspected of hosting one or more transiting planets. KOIs come from a master list of 150,000 stars which itself is generated from the Kepler Input Catalog . A KOI shows a periodic dimming, indicative of an unseen...
-157. It was later assigned the name "Kepler-11" after the Kepler spacecraft, a NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
satellite tasked with discovering planets in transit of, or crossing in front of, their stars. This transit causes a slight and regular change in the host star's brightness, which can then tested to prove the planet's existence and, later, to extrapolate the orbital parameters of the planet. Kepler-11e is first given the designation by its host star, Kepler-11. Since Kepler-11e was announced with five other planets, the letters added to the star are sorted by the planet's distance from its star. Kepler-11e is the fourth planet from Kepler-11, it is given the designation "e".
Follow-up confirmation observations were made by the Keck 1 telescope at the W.M. Keck Observatory in Hawaii, the Hale
Hale telescope
The Hale Telescope is a , 3.3 reflecting telescope at the Palomar Observatory in California, named after astronomer George Ellery Hale. With funding from the Rockefeller Foundation, he orchestrated the planning, design, and construction of the observatory, but did not live to see its commissioning...
and Shane
C. Donald Shane telescope
The C. Donald Shane telescope is a reflecting telescope located at the Lick Observatory in California. It was named after astronomer C. Donald Shane in 1978, who led the effort to acquire the necessary funds from the California Legislature, and who then oversaw the telescope's construction...
telescopes in California, the Harlan J. Smith
Harlan J. Smith Telescope
The Harlan J. Smith Telescope is a 2.7m telescope located at the McDonald Observatory, in Texas, in the United States. This telescope is one of several research telescopes that are part of the University of Texas at Austin observatory perched atop Mount Locke in the Davis Mountains of west Texas...
and Hobby-Eberly
Hobby-Eberly Telescope
The Hobby-Eberly Telescope is a 9.2-meter aperture telescope located at the McDonald Observatory. It combines a number of features that differentiate it from most telescope designs, resulting in greatly lowered construction costs...
telescopes in west Texas, the Nordic Optical Telescope
Nordic Optical Telescope
The Nordic Optical Telescope is an astronomical telescope located at Roque de los Muchachos Observatory, La Palma in the Canary Islands. First light came in 1988, with regular observing beginning in 1989. It is funded by Denmark, Sweden, Iceland, Norway and Finland...
in the Canary Islands, and by telescopes at the WIYN
WIYN Observatory
The WIYN Observatory is owned and operated by the WIYN Consortium. Its telescope, a 3.5-meter instrument, is the newest and second largest telescope on Kitt Peak in Arizona...
(including MMT
MMT Observatory
The MMT Observatory is an astronomical observatory on the site of Fred Lawrence Whipple Observatory . The Whipple observatory complex is located on Mount Hopkins, Arizona, USA in the Santa Rita Mountains...
) and Whipple
Fred Lawrence Whipple Observatory
The Fred Lawrence Whipple Observatory is an astronomical observatory owned and operated by the Smithsonian Astrophysical Observatory and is their largest field installation outside of their main site in Cambridge, MA...
observatories in Arizona. The Spitzer Space Telescope
Spitzer Space Telescope
The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...
was also used. Kepler-11's planetary system became the first discovered extrasolar system with more than three transiting planets, as well as the most compact and flattest system yet discovered, according to NASA. The planets of Kepler-11, including Kepler-11e, were announced jointly at a press conference on February 2, 2011. The findings were published in the journal Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
on February 3.
Host star
Kepler-11 is a G-type star located in the CygnusCygnus (constellation)
Cygnus is a northern constellation lying on the plane of the Milky Way. Its name is the Latinized Hellenic word for swan. One of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross...
. It has a mass of .95 Msun
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
and a radius of 1.1 Rsun, and is thus almost the same mass and radius as the Sun. With an effective temperature
Effective temperature
The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation...
of 5680 K, it is also almost as hot as the Sun, and with a metallicity
Metallicity
In astronomy and physical cosmology, the metallicity of an object is the proportion of its matter made up of chemical elements other than hydrogen and helium...
of 0, Kepler-11 is almost as metal-rich as the Sun is. Metal-rich stars tend to have easily detectable planets because higher metallicities tend to either facilitate the creation of gas giants or to promote planetary migration
Planetary migration
Planetary migration occurs when a planet or other stellar satellite interacts with a disk of gas or planetesimals, resulting in the alteration of the satellite's orbital parameters, especially its semi-major axis...
, in which the planet orbits more closely to its star. However, Kepler-11 is almost 1.73 times older than the Sun, as it has an estimated age of eight billion years. Kepler-11 is 613 parsec
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....
s away from the Earth; its distance contributes to its apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of 14.2 (V). It, thus, cannot be seen with the naked eye
Naked eye
The naked eye is a figure of speech referring to human visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered "naked"...
. Other than Kepler-11e, Kepler-11 is the host star of the planets Kepler-11b
Kepler-11b
Kepler-11b is an exoplanet discovered in the orbit of the star Kepler-11 by the Kepler spacecraft, a NASA-led mission to discover Earth-like planets. Kepler-11b is four times more massive and twice as large as Earth, but it has a lighter density estimated at a little over half Earth's, and is...
, Kepler-11c
Kepler-11c
Kepler-11c is an exoplanet discovered in the orbit of the sun-like star Kepler-11 by the Kepler spacecraft, a NASA telescope aiming to discover Earth-like planets. It is the second planet from its parent star, and is most likely a water planet with a thin hydrogen–helium atmosphere. Kepler-11c...
, Kepler-11d
Kepler-11d
Kepler-11d is an exoplanet discovered in the orbit of the sun-like star Kepler-11. It is named for the telescope that discovered it, a NASA spacecraft named Kepler that is designed to detect Earth-like planets by measuring small dips in the brightness of their host stars as the planets cross in front...
, Kepler-11f
Kepler-11f
Kepler-11f is an exoplanet discovered in the orbit of the sunlike star Kepler-11 by NASA's Kepler spacecraft, which searches for planets that transit their host stars. Kepler-11f is the sixth planet from its star, orbiting one fourth of the distance of the Earth from the Sun every 47 days...
, and Kepler-11g. The inner five planets in the system orbit in a tightly knit configuration that would fit within the orbit of planet Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
, while Kepler-11g, compared to its inner sister planets, orbits at a much further distance.
Characteristics
Kepler-11e, which formed within the first few million years of the star system's formation, has a mass 8.4 times that of Earth's, and radius 4.52 times that of Earth's. With a density of 0.5 grams/cm3, Kepler-11e has a density that is half of that of pure waterPurified water
Purified water is water from any source that is physically processed to remove impurities. Distilled water and deionized water have been the most common forms of purified water, but water can also be purified by other processes including reverse osmosis, carbon filtration, microfiltration,...
at standard temperature and pressure
Standard conditions for temperature and pressure
Standard condition for temperature and pressure are standard sets of conditions for experimental measurements established to allow comparisons to be made between different sets of data...
and slightly less than the density of Saturn. Kepler-11e has a surface equilibrium temperature of 617 K, and is thus has an equilibrium temperature approximately 2.4 times hotter than Earth's. Kepler-11e orbits its star at a mean distance of .194 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, making it the fourth planet from its star. It completes an orbit every 31.995990 days. In comparison, Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
orbits the Sun every 87.97 days at a distance of .387 AU. Kepler-11e's orbital inclination
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
is 88.8°, making it almost entirely edge-on to its star as seen from Earth.
Because it isn't as close to its star as its sister planets Kepler-11b
Kepler-11b
Kepler-11b is an exoplanet discovered in the orbit of the star Kepler-11 by the Kepler spacecraft, a NASA-led mission to discover Earth-like planets. Kepler-11b is four times more massive and twice as large as Earth, but it has a lighter density estimated at a little over half Earth's, and is...
and Kepler-11c
Kepler-11c
Kepler-11c is an exoplanet discovered in the orbit of the sun-like star Kepler-11 by the Kepler spacecraft, a NASA telescope aiming to discover Earth-like planets. It is the second planet from its parent star, and is most likely a water planet with a thin hydrogen–helium atmosphere. Kepler-11c...
, the Kepler team suggests that its light density may come from a large hydrogen and helium atmosphere that has not been blown away by the stellar wind
Stellar wind
A stellar wind is a flow of neutral or charged gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric.Different types of stars have...
.